1. Systems and Feedback Loops

2. Questions for Today: What is a system and it’s parts?
What are the different types of system response? (Positive and Negative Feedback Loops)
What is synergy and how is it harmful and beneficial?

3. The environment is difficult to study because…
A hypothesis must be testable
VARIABLES must be controlled and isolated
Too many interactions – known & unknown

4. More problems Scale is often a problem Measurement is difficult
Populations over time
Environmental factors over centuries
Measurement is difficult
Species, pollutants, tons of soil

5. We do our best… At best, we provide trends & estimates Rely on models
Examples include climate models, ocean models, atmospheric models, etc.

6. Models A representation or simulation of a system being studied
Can be mental, physical, graphical, mathematical, conceptual

7. Correlation Relationship between two separate events
More CO2 and higher global temperatures

8. Correlation DOES NOT mean causation…
More lemons imported causes more traffic accidents?

9. Parts of a System
A system is a set of components that function and interact in some regular way.
Parts of a system
Inputs
Flows or thoroughputs
Outputs
Environmental scienctists use computer modeling to analyze systems.

10. System Vocabulary INPUT THROUGHPUT OUTPUT
 matter, energy, information entering a system
THROUGHPUT
 rate flow of matter, energy, or information through a system
OUTPUT
 matter, energy, information leaving a system
Stuff goes in
Stuff is processed
Stuff comes out

11. Energy Inputs Throughputs Outputs Energy resources Heat Matter
Waste and
pollution
Economy
Figure 2.10
Inputs, throughput, and outputs of an economic system. Such systems depend on inputs of matter and energy resources and outputs of waste and heat to the environment. Such a system can become unsustainable if the throughput of matter and energy resources exceeds the ability of the earth’s natural capital to provide the required resource inputs or the ability of the environment to assimilate or dilute the resulting heat, pollution, and environmental degradation.
Goods and
services
Information
Fig. 2-10, p. 44

12. Input  Throughput  Output

13. FEEDBACK LOOPS Change induces change Feedback Loop Stuff is processed
Stuff goes in
Stuff is processed
Stuff comes out

14. Feedback Loops
Systems respond to change through the use of feedback loops
Two types of feedback loops:
Positive – process that increases change
Negative - process that decreases change
Homeostasis

15. Negative Feedback Loops
The change counteracts the situation
Examples:
What happens when you’re hot?
What happens when you’re cold?

16. Negative Feedback Loops
Negative, or corrective, feedback loops causes a system to change in the opposite direction from which it is moving.
Examples:
Thermostat
Recycling

17. Temperature reaches desired setting and furnace goes off
House warms
Temperature reaches desired setting
and furnace goes off
Furnace on
Figure 2.12
Negative feedback loop. When a house being heated by a furnace gets to a certain temperature, its thermostat is set to turn off the furnace, and the house begins to cool instead of continuing to get warmer. When the house temperature drops below the set point, this information is fed back, and the furnace is turned on and runs until the desired temperature is reached. The system receives feedback that reverses the process of heating or cooling.
House cools
Temperature drops below desired setting
and furnace goes on

18. Positive feedback Loops
The change compounds the situation = Snowball Effect!
Example:
As long as there are more human births than deaths, population will continue to increase.

19. Positive Feedback Loops
A feedback loop occurs when an output of matter, energy, or information, is fed back into the system as an input and leads to changes in that system.
A positive feedback loops causes a system to change further in the same direction.
Examples of Harmful Feedback loops:
Deforestation
Melting of Polar Ice Caps
Examples of Beneficial Feedback Loops:
Blood Clotting
Ecological Succession

20. Decreasing vegetation...
...which causes
more vegetation
to die.
...leads to
erosion and
nutrient loss...
Figure 2.11
Positive feedback loop. Decreasing vegetation in a valley causes increasing erosion and nutrient losses, which in turn causes more vegetation to die, which allows for more erosion and nutrient losses. The system receives feedback that continues the process of deforestation.
Fig. 2-11, p. 45

21. Pesticides:

22. Urban Sprawl

23. Synergy
Synergy is when two or more process interact so that the combined effects are greater than the sum of their separate effects.
Harmful Example:
Smoking and Asbestos leading to Lung Cancer
Air Pollutant Cocktails
Beneficial Example:
Writing your Congressmen (Cheesy, Huh?)

24. Positive or Negative 1 person in a group of 10 has a cold.
That person passed the cold to another and soon 5 people now have the cold.
Those 5 students then each pass the cold to another.

25. Feedback Loops in Context
Global warming says that the average temperature of Earth is increasing. During analysis, scientists have identified possible positive and negative feedback loops to explain atmospheric climate change.

26. Radiation and Reflection
ANALOGY: Students should think about a parked car gaining heat in its interior. The heat from the sun coming in gets trapped and makes the car hotter inside than the outside temp. What are ways to reduce that? Those reflective sun shields, cracking the windows. 26

27. Positive or Negative?
The warming of the oceans causes dissolved CO2 to bubble out into the atmosphere. This atmospheric CO2 helps to trap heat near the earth. This trapped heat continues to warm the ocean.

28. Positive or Negative?
Warmer water temperatures cause greater water evaporation, which puts more water vapor in the air. More water vapor in the air traps heat inside the atmosphere.

29. Positive or Negative?
The increased cloud cover from the last example might also act to reflect sunlight back into space, preventing it from entering our atmosphere. This might cool the earth.

30. Positive or Negative?
Sunlight striking the earth is absorbed by dark colors and reflected by light colors. The polar ice caps act like huge mirrors, reflecting sunlight back into space. Warmer water temperatures are melting these ice caps and decreasing these big “mirrors,” leaving dark water behind.

31. Positive or Negative?
Warmer temperatures cause greater water evaporation, which falls to earth as precipitation. Therefore global warming may cause increased snow fall in the polar regions, leading to increased snow and ice formation.

32. How did you do? 1. Positive 2. Positive 3. Negative 4. Positive

33. Contemplate this…
What would Earth look like if there weren't any greenhouse effect at all?
It would probably look a lot like Mars.
Mars doesn't have a thick enough atmosphere to reflect enough heat back to the planet, so it gets very cold there.

34. Hmmmmm….
Some scientists have suggested that we could terraform the surface of Mars by sending "factories" that would spew water vapor and carbon dioxide into the air.
If enough material could be generated, the atmosphere might start to thicken enough to retain more heat and allow plants to live on the surface.

35. Just like early Earth…
Once plants spread across Mars, they would start producing oxygen.
After a few hundred or thousand years, Mars might actually have an environment that humans could simply walk around in
-- all thanks to the greenhouse effect.
Early earth (3.5bya) did not have oxygen. Life as we understand it didn’t start until we had plants. Prior to photosynthesis, life sustained itself with chemosynthesis and sulfur. Might pollution cause us to undergo another major evolutionary switch???? 35